1. Field of the Invention
The present invention relates generally to dual fuel power generation systems employing one or more turbine engines. In another aspect, the invention concerns a dual fuel turbine system which can be powered by combusting natural gas and/or a gaseous fuel mixture of a light hydrocarbon and steam in the burner(s) of the turbine.
2. Description of the Prior Art
Coal-fired electrical power generation plants typically have an operating efficiency of about 30 to about 40 percent. In contrast, combined cycle electrical power plants, employing gas turbine engines and heat recovery, typically have an operating efficiency of about 40 to about 60 percent. Combined cycle power plants are also much less expensive to design and build than coal-fired plants. Because of these and other advantages, combined cycle power plants have been employed worldwide to provide electrical power for commercial and residential use. Similarly, the gas turbine or combined cycle plants can drive mechanical components like compressors.
To enhance the reliability of power generation, electrical utilities typically require combined cycle power plants to employ dual fuel systems for powering the turbine engine(s). Such dual fuel systems typically employ a gaseous fuel (e.g., natural gas) and a liquid fuel (e.g., distillate oils). The gaseous fuel is used to power the turbine under normal operating conditions, while the liquid fuel can be stored on site and used to power the turbine when the gaseous fuel is temporarily unavailable or when demand and/or price for the gaseous fuel is high. For example, when the weather turns cold the demand for natural gas as heating fuel and as fuel for electricity generation is very high. In such a situation, the liquid fuel can be used to power the turbine engine and generate electricity in a more reliable and/or cost-effective manner.
The dual fuel capability of combined cycle power plants requires additional construction, operation, and maintenance expenditures versus single fuel combined cycle power plants. For example, in dual fuel combined cycle power plants, both the gaseous fuel and the liquid fuel must have their own individual fuel control, distribution, and injection systems because the vastly different flow and combustion properties of the gaseous and liquid fuel make it virtually impossible to effectively control, distribute, and inject the fuels with the same fuel delivery system. Further, after the liquid fuel has been used to power the turbine engine, the liquid fuel delivery system must be thoroughly cleaned to prevent carbonaceous “gum,” or worse yet solid deposits, from building up in the liquid fuel delivery system.